全文获取类型
收费全文 | 1602篇 |
免费 | 1篇 |
专业分类
化学工业 | 4篇 |
建筑科学 | 1篇 |
轻工业 | 4篇 |
冶金工业 | 1591篇 |
自动化技术 | 3篇 |
出版年
2019年 | 1篇 |
2018年 | 1篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2006年 | 1篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2003年 | 3篇 |
1999年 | 47篇 |
1998年 | 481篇 |
1997年 | 265篇 |
1996年 | 200篇 |
1995年 | 94篇 |
1994年 | 78篇 |
1993年 | 98篇 |
1992年 | 15篇 |
1991年 | 21篇 |
1990年 | 22篇 |
1989年 | 23篇 |
1988年 | 22篇 |
1987年 | 43篇 |
1986年 | 24篇 |
1985年 | 28篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1978年 | 1篇 |
1977年 | 31篇 |
1976年 | 68篇 |
1955年 | 1篇 |
排序方式: 共有1603条查询结果,搜索用时 9 毫秒
931.
932.
933.
934.
935.
936.
We have examined the gel profiles of staphylococcal nuclease digests of intact nuclei following different extents of removal of histone H1 by low pH. It was found that the submonomer fragment pattern (i.e. fragments less than 140 base pairs (bp) changed dramatically following removal of H1. The most striking feature of this change was a marked increase in the relative intensity of a band migrating at 102 +/- 4 bp when about 20-50% of the nuclear DNA is rendered acid soluble. All other submonomer bands decreased in relative intensity. There was no evidence for an approximately 100-bp repeat pattern accompanying the enhanced generation of the 102-bp fragment following H1 removal. This result, along with the comparisons of gel profiles for different extents of digestion, suggests that removal of histone H1 from nuclei results in an increased susceptibility of the DNA to staphylococcal nuclease at one or both ends of many of the core particles and that a strong block to further digestion occurs within these core particles resulting in the formation of a relatively stable 102-bp fragment. 相似文献
937.
The effects of large and oral doses of ascorbic acid on renal clearance and excretion of uric acid were studied in nongouty subjects because ascorbic acid has been reported to increase renal uric acid clearance. Our results indicate that 4 or 12 gm ascorbic acid taken in divided doses had no effect on serum uric acid concentration or uric acid excretion and clearance by the kidney. Reasons for these results, which differ from previous reports, are discussed. We quantitated the magnitude of the interference of ascorbic acid in the measurement of uric acid by the nonspecific methods frequently used, since falsely elevated urine uric acid could lead to misinterpretation of screening tests. 相似文献
938.
939.
MS Ansari WJ Miller MW Neathery JW Lassiter RP Gentry RL Kincaid 《Canadian Metallurgical Quarterly》1976,152(2):192-194
Zinc metabolism and homeostasis were studied in young growing rats fed a 38 ppm zinc diet with added zinc levels ranging from 0 to 8400 ppm for 21 days. High dietary zinc did not cause toxicity symptoms. Stable zinc in feces increased linearly with dietary zinc intake but fecal 65Zn, from a single oral dose, did not increase above the 1200 ppm dietary level. Stable zinc in liver, kidney, and tibia increased two to three times with 2400 ppm added zinc, but was not further elevated until 8400 ppm was fed. Stable zinc in muscle and heart was not affected appreciably by dietary zinc level. In all tissues, 65Zn retention was drastically reduced with 1200 ppm added dietary zinc. Additional dietary zinc reduced 65Zn in muscle and heart but had little effect on liver and kidney 65Zn. The data indicate that rats have fairly effective homeostatic control mechanisms for tissue zinc below about 7200 ppm dietary zinc. Whereas, with dietary zinc up to about 1200 ppm, decreasing absorption is the main route of homeostatic control, above this level, more rapid zinc turnover rates and increasing endogenous zinc excretion appear to have major importance. 相似文献
940.
Large numbers of a reovirus-like agent were visualized with electron microscopy in bacteria-free gut homogenates obtained from piglets with a fatal diarrhea resembling transmissible gastroenteritis. The syndrome, of vomiting, diarrhea, dehydration, and death, was reproduced in piglets artificially infected with these bacteria-free gut homogenates. Reovirus-like particles persisted in serial piglet passage and none was seen in uninfected, asymptomatic controls. Hyperimmune sera (made in recovered piglets) aggregated the reovirus-like particles, as judged by immunoelectron microscopy, and neutralized the infectious agent. The cytoplasm in enterocytes on infected intestinal epithelium fluoresced when this hyperimmune sera was used in an indirect fluorescent antibody test. Feeding cow colostrum or diets containing porcine gamma globulin protected infected piglets. No cytopathogenic effect was noted in infected tissue cultures, nor did this agent affect neonatal guinea pigs, hamsters, mice, and rats. The agent did not agglutinate human O or A erythrocytes. 相似文献